Porous Single-Layer Polymer Membrane with Uniform Pore Formation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing membrane production processes struggle to create asymmetric ultrafiltration membranes with high surface porosity and a small difference between surface and total porosity, leading to performance issues such as faster blockage and reduced permeability due to abrupt pore size changes and low surface porosity.
Innovation Solution
A process involving a membrane-forming casting solution and a non-precipitating protective solution is applied to a support, followed by contact with a precipitating agent and removal of the protective layer, resulting in a single-layer polymer membrane with high surface porosity and controlled phase separation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional phase separation processes (NIPS, VIPS, EIPS, TIPS) are used to produce filtration membranes, then membrane formation is achieved through demixing of casting solution, but the resulting membranes exhibit low surface porosity and abrupt pore size changes between layers
Solution Approach 1:
The invention applies a protective layer to the casting solution before phase separation occurs. This protective layer prevents direct contact between the casting solution and the precipitating agent during the critical initial phase separation stage, thereby controlling pore formation and preventing abrupt pore size changes. The protective layer is subsequently removed to reveal the improved membrane structure.
Solution Approach 2:
The protective layer acts as an intermediary substance between the casting solution and the precipitating agent. It mediates the phase separation process by controlling the interaction between these two components, enabling gradual and uniform pore size development rather than abrupt changes. This intermediary layer is temporarily present during manufacturing but not in the final product.
2Reliability
If co-casting of multiple casting solution layers is used to enlarge pores and increase flow rate, then surface porosity is improved, but the overall membrane thickness increases and layer delamination risk occurs
Solution Approach 1:
The invention extracts and removes the protective layer after it has served its function during phase separation. This removal step eliminates the temporary protective layer while retaining the benefits it provided during manufacturing, resulting in a single-layer membrane without the complexity of multi-layer structures or residual protective materials.
Solution Approach 2:
The invention changes the physical and chemical parameters of the casting solution system by introducing a protective layer with specific properties (solvent compatibility, viscosity, thickness). This parameter change enables control over the phase separation process and pore structure development without requiring multiple casting layers, thereby simplifying the overall membrane structure while maintaining improved filtration performance.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The process achieves a single-layer membrane with surface porosity of at least 40% and total porosity 0.8 to 1.4 times the surface porosity, enhancing filtration performance and reducing the risk of blockage.
Implementation Method 1
The casting solution composition or the thermodynamic state of the casting solution is then altered until demixing/phase separation is achieved. Phase separation results in an integral phase with a coherent solid component.
Implementation Method 2
essentially, four different mechanisms for initiating phase separation are distinguished: (1) non-solvent induced phase separation (NIPS), (2) vapor-induced phase separation (VIPS), (3) evaporation-induced phase separation (EIPS), and (4) thermally induced phase separation (TIPS)
Implementation Method 3
The protective solution comprises 2-pyrrolidone or a non-membrane-forming polymer (surrogate polymer) selected from the group consisting of polyvinylpyrrolidone, polyethylene glycol, polysaccharides and/or polyvinyl alcohol, and a solvent therefor.
Data Source
Figure 1
Figure 2
Figure 3
AI summary
The present invention relates to a method for producing a porous single-layer polymer membrane, to a porous single-layer polymer membrane and to the use of the polymer membrane for filtration.